The author of a book about the 1955 murder of black teenager Emmett Till in Mississippi has been contacted by FBI agents asking about his interview with a witness who acknowledged lying about her interactions with the boy, it has emerged.

The author of a book about the 1955 murder of black teenager Emmett Till in Mississippi has been contacted by FBI agents asking about his interview with a witness who acknowledged lying about her interactions with the boy, it has emerged.

North Carolina author Timothy Tyson said he turned over interview recordings and other research materials for his 2017 book on the case that shocked the nation and helped build momentum for the civil rights movement in America.

Hours after news broke about a renewed investigation prompted by the book, The Blood Of Emmett Till, Mr Tyson told reporters that he supports a fresh look at “one of the most notorious racial incidents of racial violence in the history of the world” – but does not think his research alone will provide enough evidence for new charges.

The Duke University scholar said: “It’s possible that the investigation will turn up something. But there’s nothing that I know of, and nothing in my research, that is actionable, I don’t think.”

However, he said investigators may be able to link it to other material in their possession.

The book quotes a white woman, Carolyn Donham, as saying during a 2008 interview that she was not truthful when she testified that the black 14-year-old had grabbed her, whistled and made sexual advances at a Mississippi store six decades ago.

Carolyn Donham, then known as Carolyn Bryant and a potential witness to the killing, has acknowledged lying (AP)

A federal official said information in the 2017 book was what led federal investigators to re-examine the case.

The reopening of the Till case was disclosed in a federal report sent to members of congress in March that said the Justice Department had received unspecified “new information”. The report’s contents were not widely known until Thursday.

The case was closed in 2007, with authorities saying the suspects were dead.

The prosecutor with jurisdiction over the Mississippi community where Till was abducted, District Attorney Dewayne Richardson, declined to comment on whether federal authorities had given him new information since they reopened the investigation. The Justice Department also declined to comment.

It is unclear what new charges could result from a renewed investigation, said Tucker Carrington, a professor at the University of Mississippi law school.

Conspiracy or murder charges could be filed if anyone still alive is shown to have been involved, he said, but too much time likely has passed to prosecute anyone for other crimes, such as lying to investigators or in court.

Two white men – Ms Donham’s then-husband, Roy Bryant, and his half brother, JW Milam — were charged with the boy’s murder but acquitted.

Emmett Till was from Chicago, but had been staying with relatives in northern Mississippi when he was killed.

The men later confessed to the crime in a magazine interview but were not retried. Both are now dead.

Ms Donham, who turns 84 this month, lives in Raleigh, North Carolina. A man who came to the door at her residence declined to comment about the investigation.

Deborah Watts, co-founder of the Emmett Till Legacy Foundation, said it is wonderful her cousin’s killing is getting another look but declined to discuss details, saying: “None of us wants to do anything that jeopardises any investigation.”

Abducted from the home where he was staying, Till was beaten and shot, and his body was found weighted down with a cotton gin fan in a river.

His mother, Mamie Till Mobley, had his casket left open. Images of his mutilated body graphically illustrated the depth of racial hatred in the Deep South and inspired civil rights campaigns.

A Mississippi Freedom Trail marker recaps the significance of the shop where the fateful encounter is alleged to have taken place (AP)

Ms Donham, then 21 and known as Carolyn Bryant, testified in 1955 as a prospective defence witness in the trial of Bryant and Milam.

With jurors out of the courtroom, she said a “n***** man” she did not know took her by the arm in the store.

“He said: ‘How about a date, baby?'” she testified, according to a trial transcript released by the FBI a decade ago.

Ms Bryant said she pulled away, and moments later the young man “caught me at the cash register”, grasping her around the waist with both hands and pulling her toward him.

A judge ruled the testimony inadmissible. An all-white jury freed her husband and the other man even without this evidence.

In his book, Mr Tyson wrote that Ms Donham told him her testimony about Emmett Till accosting her was not true.

She is quoted as saying: “Nothing that boy did could ever justify what happened to him.”